Re: Grrrr ... dhcpd6

[Pavel Simerda <psimerda redhat com>]

----- Original Message -----
> From: "Bjørn Mork" <bjorn mork no>
> To: "Gene Czarcinski" <gene czarc net>
> Cc: networkmanager-list gnome org
> Sent: Friday, September 28, 2012 10:46:31 AM
> Subject: Re: Grrrr ... dhcpd6
> 
> Gene Czarcinski <gene czarc net> writes:
> 
> > OK, anyone have any experience sending commands, requests etc. via
> > dhclient?
> 
> Well, if you ask me (OK, you didn't, but I am answering anyway :-)
> then
> the IPv6 support in the ISC dhclient is far from mature enough to be
> used for anything yet, and it moves at a pace which... I don't think
> it
> will ever become useful outside simple lab experiments.  The PD
> support
> is unconfigurable.  There is no support for PPP interfaces. Both of
> these are show stoppers.  IMHO, you have *no* DHCPv6 support worth
> mentioning without them.

The basic DHCP usecases are covered by dhclient.

> And this is not because these features are difficult to add.  There
> have
> been feature requests and patches circulating for years.  Here's one
> example:
> https://lists.isc.org/pipermail/dhcp-users/2010-April/011624.html

Then the fist step might be to get the patchset into distributions if
it's good enough to be added. It can be used for a while and then
submitted again for inclusion. Poking jpopelka for that.

> Being able to configure an IA_NA address on an ethernet interface is
> just not enough.

It's one of the two most important features of DHCPv6, the other being
conveying DNS information to hosts that also works.

> Look further and plan for the other features you
> *must* support. 

Could you please specify which of the features are required in host
implementations? Currently I only know about the options Gene is trying
to use. But that looks to me too easy to be a good reason to abandon
dhclient.

> Using the ISC dhclient is a dead end.
> 
> I believe the ISC development model just does not work anymore.  It
> belongs in another millennium.  Sorry.

You *may* be right. But, unfortunately, I have been playing with DHCPv6
implementations and there wasn't one that I would actually like. Except
ISC DHCP which works for me but needs improvement.

> Hmm, looking at https://bugzilla.redhat.com/show_bug.cgi?id=626514 it
> seems that Redhat is using a heavily patched ISC dhclient, fixing
> these shortcomings.

And this can continue and distributions are free to include the patches.

> But I wonder if they are prepared to take over as upstream?  If not,
> then I suggest that NM development look for other
> options,

I would like to see one single option that matches or even exceeds the
quality of ISC DHCP, which is not perfect, but still rather good. Look
at the RH-patched version.

> or the DHCPv6 support will be unmaintainable on any non Redhat distribution.

To summarize the possibilities:

1) Continue using ISC DHCP. Integrate the necessary patches upstream.

2) Use a fork of ISC DHCP that integrates the patches. Or maintain a
cross-distro patchset.

3) Find/create a real DHCP client (even dhclient doesn't work as a DHCP client
without NetworkManager's dhclient-script).

I'm all for taking the best route. But... dhclient works pretty well for most
common use cases. And we're not going to make default anything that breaks
those.

And if we're pushing such a big change, I would only ever go for a proper solution.
The new DHCP client should work well for the current use cases and bring improvement
to new use cases. And it should really work as a DHCP client and should *not*, at
least with proper commandline option, try to be a network configuration daemon.

The only goal of a DHCP client for the modern networking is to maintain the DHCP state
and convey the DHCP configuration changes to the network configuration daemon. Again,
dhclient does it, but only with NetworkManager's dhclient-script.

Cheers,

Pavel

> 
> 
> Bjørn
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